In 1908 William Howard Taft, Roosevelt's personal choice for the Republican nomination, was elected President. Although Taft continued much of Roosevelt's program, he was basically a conservative. Not adept at the art of politics, he alienated Republican progressives, who prepared to support Robert M. La Follette of Wisconsin against him for the Republican nomination for President in 1912. Roosevelt, instead of supporting La Follette, sought the nomination for himself.

When Taft won the nomination Roosevelt left the party to become the candidate of the newly formed Progressive, or Bull Moose, party. This split in the Republican forces enabled the Democratic candidate, Woodrow Wilson, to win the election.